1. Field
The present invention relates to a positioning device for positioning of movable object, a lithographic apparatus and a method for manufacturing a device.
2. Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon substrate). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In the known lithographic apparatus, a magnetic positioning device is used for the positioning of a substrate stage. In such apparatus, one or more coils cooperate with a number of magnets to actuate the substrate stage to a desired position.
In a known embodiment of such device the coils are arranged in a coil assembly attached to the substrate stage, while the magnets are included in a permanent magnet plate which is arranged substantially stationary next to the operation area of the substrate stage. An example of such arrangement is for instance disclosed in U.S. 2005/0077786, the contents of which is herein incorporated by reference. In this embodiment, the magnetic positioning apparatus is used for the coarse positioning of a long stroke module of the substrate stage. The long stroke module supports a short stroke module which is configured to carry a substrate. A high accuracy actuation device is provided between the long stroke module and the short stroke module to position the substrate supported on the short stroke module with high accuracy.
In an alternative embodiment of a magnetic positioning device, magnets are attached to the substrate stage, and coils are provided at a substantially stationary location next to the operation area. An example of the latter arrangement can for instance be found in U.S. Pat. No. 5,196,745, the contents of which is herein incorporated by reference. In the device of U.S. Pat. No. 5,196,745 a plurality of stage-attached permanent magnetic arrays are provided. Each of the magnetic arrays includes a series of adjacent oppositely poled permanent magnets that cooperate with stationary coil arrays in the horizontal plane to produce the proper lateral forces to move the substrate stage in the desired direction. The above-mentioned alternative embodiment of the magnetic positioning device has a benefit that since the magnets are provided on the substrate stage and the coils are arranged at a stationary position, the cables for energizing the coils do not have to be guided to the moving stage.
In certain lithographic apparatuses, two substrate stages are provided which can be moved in a substantially common operation area. Due to the presence of two substrate stages, the throughput of such dual stage lithographic apparatus can be substantially higher than a single stage lithographic apparatus.
In view of the above-mentioned benefit of the alternative embodiment of the magnetic positioning device, or an other suitable reason, it may desirable to use this alternative embodiment for the actuation of the two substrate stages of a dual stage lithographic apparatus. However, when two substrate stages have to move in a common operation area the alternative embodiment as proposed in U.S. Pat. No. 5,196,745 cannot be applied as the stationary coil arrays cannot be used to simultaneously actuate both the first substrate stage and the second substrate stage.